This section provides backrgound information related to the present disclosure which is not necessarily prior art.
The term decorative panel in the sense of the disclosure means wall, ceiling, door or floor panels comprising a decoration applied onto a carrier plate. Decorative panels are used in a variety of ways both in the field of interior design of rooms and for decorative claddings of buildings, for example in exhibition stand construction. One of the most common application fields of decorative panels is their use as a floor covering. Herein, the decorative panels often comprise a decoration intended to replicate a natural material.
Examples of such replicated natural materials are wood species such as maple, oak, birch, cherry, ash, walnut, chestnut, wenge or even exotic woods such as Panga-Panga, mahogany, bamboo and bubinga. In addition, often natural materials such as stone surfaces or ceramic surfaces are replicated.
Heretofore, such decorative panels have often been produced as laminates in which a decorative paper preprinted with a desired decoration is applied onto a carrier plate and in turn a so-called overlay is applied onto the decorative paper. In order to avoid a deformation of the decorative panels, the so-called cupping, by shrinkage effects of the applied decorative paper subsequently a backing paper is applied on the side of the carrier plate opposite to the decorative paper and the layered structure obtained is fixedly bonded together by use of appropriate pressure and/or heat-activated adhesives. The forces acting on the carrier plate by the backing paper thereby should counteract the tensile forces caused by the cupping.
The application of the backing layer implies a further working step and thus further production costs.
The term “direct printing” in the sense of the disclosure means the application of a decoration directly onto the carrier of a panel or onto an unprinted fiber material layer applied to the carrier. In contrast to conventional methods in which a decorative layer previously printed with a desired decoration is applied onto the carrier, in direct printing the decoration is printed directly in the course of the surface coating or panel manufacturing process. Here, different printing techniques such as flexographic printing, offset printing or screen printing may be used. In particular, digital printing techniques such as inkjet processes or laser printing can be used.
In the sense of the disclosure the term “fiber materials” means materials such as paper and nonwoven fabrics on the basis of plant, animal, mineral or even synthetic fibers as well as cardboards. Examples of fiber materials on the basis of plant fibers in addition to papers and nonwoven fabrics made of cellulose fibers are boards made of biomass such as straw, maize straw, bamboo, leaves, algae extracts, hemp, cotton or oil palm fibers. Examples of animal fiber materials are keratin-based materials such as wool or horsehair. Examples of mineral fiber materials are mineral wool or glass wool.
For protecting the applied decorative layer normally wearing or top layers are applied on top of the decorative layer. A wearing and/or top layer in the sense of the disclosure is a layer applied as an outer border which in particular protects the decorative layer from wear or damage caused by dirt, moisture and mechanical impacts such as abrasion.
It is often intended to introduce a surface structure matching with the decoration in such a wearing or top layer. A surface structure matching with the decoration means that the surface of the decorative panel has a haptically perceivable structure which with respect to its shape and pattern corresponds to the applied decoration in order to achieve a reproduction of a natural material as close to the original as possible even with respect to the haptic.
A problem which may occur during direct printing of decorative panels is that the surface of the decorative panel to be printed is no optimal printing subsurface onto which a corresponding decoration can be applied. This may be the case in direct printing of the carrier as well as in printing a fiber material applied onto the carrier.
Thus, for example, during the production of the decorative panel, such as during the structuring of the top layer by means of a press, the effect may occur that the top layer does not sufficiently adhere to the subsurface and thus the surface is damaged.
When printing a fiber material applied to the carrier a problem may arise that a paper or nonwoven layer applied as a subsurface onto the carrier plate of a decorative panel is penetrated by the resin used for the application in such a way that the resin applied for the attachment soaks through on the side of the paper or nonwoven fabric intended for printing and may lead there to adhesion problems of the printing ink. In order to overcome this problem it may be provided to provide the paper or nonwoven fabric with a barrier layer which prevents the soaking through of the resin. However, such a barrier layer often leads to the fact that the ink applied during the printing does not or not sufficiently penetrate into the paper or nonwoven but remains on the surface which adversely affects the quality of the print. Furthermore, it may be provided that the paper or nonwoven fabric prior to the application onto the carrier plate is provided with a paint receiving layer on the side to be printed which subsequently is printed. The thus prepared decoration paper is then applied onto the carrier plate. During the subsequent application of a top or wearing layer then adhesion problems may occur, so that the final laminate composite does not have sufficient stability and, for example, a splitting of the laminate in the decoration paper layer may occur.